package com.hmdp.utils;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.hmdp.entity.Shop;
import org.springframework.context.annotation.Bean;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;

import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.function.Function;


@Component
public class CacheClient {
    private final StringRedisTemplate stringRedisTemplate;

    private static final ExecutorService CACHE_REBUILD_EXECUTOR= Executors.newFixedThreadPool(10);

    public CacheClient(StringRedisTemplate stringRedisTemplate) {
        this.stringRedisTemplate = stringRedisTemplate;
    }


    public void set(String key, Object value, Long time, TimeUnit unit){
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(value),time,unit);
    }

    public void setWithLogicalExpire(String key, Object value, Long time, TimeUnit unit){
        RedisData redisData = new RedisData();
        redisData.setData(value);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(unit.toSeconds(time)));
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(redisData));
    }

    public <R,ID> R queryWithPassThrough(String keyPrefix, ID id, Class<R> type,
                                         Function<ID,R> dbFallBack,Long  CACHE_NULL_TTL,TimeUnit unit){
        String key= keyPrefix +id;
//        1.从redis查询店铺缓存
        String json = stringRedisTemplate.opsForValue().get(key);

//        2、判断是否存在
        if (StrUtil.isNotBlank(json)){
//        3、存在直接返回

            return JSONUtil.toBean(json, type);
        }
        if (json!=null){
            return null;
        }
//        4、不存在，根据id查询数据库

        R r=dbFallBack.apply(id);
        if (r==null){
//        5、不存在，抛出错误
            stringRedisTemplate.opsForValue().set(key,"",CACHE_NULL_TTL,unit);
            return null;
        }
//        6、存在，写入redis
        this.set(key,r,CACHE_NULL_TTL,unit);
        return r;
    }

    public <R,ID> R queryWithLogicalExpire(String keyPrefix,ID id,Class<R> type,
                                           Function<ID,R> dbFallBack,Long  CACHE_NULL_TTL,TimeUnit unit){
        String key= keyPrefix +id;
//        1.从redis查询店铺缓存
        String json = stringRedisTemplate.opsForValue().get(key);
//        2、判断是否存在
        if (StrUtil.isBlank(json)){
//        3、不存在直接返回
            return null;
        }
//        4、命中需要json反序列化为对象
        RedisData redisData = JSONUtil.toBean(json, RedisData.class);
        R r=JSONUtil.toBean((JSONObject) redisData.getData(), type);
        LocalDateTime expireTime = redisData.getExpireTime();

//        5、判断是否过期，未过期就直接返回店铺信息，过期就缓存重建
        if (expireTime.isAfter(LocalDateTime.now())){
            return r;
        }

//        6、缓存重建，获取互斥锁，判断是否获取成功
        String lockKey=RedisConstants.LOCK_SHOP_KEY+id;
        if (tryLock(lockKey)) {
//        成功就开启新独立线程实现缓存重建
//            使用线程池，异步执行，防止阻塞主线程
            CACHE_REBUILD_EXECUTOR.submit(()->{
                try {
                    R r1 = dbFallBack.apply(id);
                    this.setWithLogicalExpire(key,r1,CACHE_NULL_TTL,TimeUnit.SECONDS);
                }catch (Exception e){
                    throw new RuntimeException(e);
                }
                finally {
                    unLock(lockKey);
                }
            });
        }
//        失败就直接返回过期信息
        return r;
    }
    private boolean tryLock(String key){
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }

    private  void unLock(String key){
        stringRedisTemplate.delete(key);
    }


}
